Field of the Present Invention
The present invention relates to a dope dyed sea-island type conjugate multifilament and a process of preparing such conjugate multifilament which can improve light fastness and wash fastness when producing woven and knitted fabrics.
The sea-island type conjugate multifilament is produced by conjugate spinning a easy soluble polymer as a sea component and a fiber forming polymer as an island component into a sea-island type. It is mainly made for the purpose of producing an ultra-fine fiber. In other words, after producing the sea-island type conjugate multifilament, the sea component is dissolved by treating the multifilament with an alkali solution or the like to thus produce an ultra-fine fiber only composed of the island component.
In this way, as compared to a process of preparing a ultra-fine fiber by direct spinning, the process of preparing a ultra-fine fiber from the sea-island type conjugate multifilament has excellent spinning and drawing processability and can obtain a ultra-fine fiber of a finer denier. Meanwhile this method requires a process of dissolving and removing the sea component polymer using an organic solvent in a finishing process after weaving or knitting operations. Thusly it is very important for the sea component polymer to have a property of being easy soluble in an organic solvent or solution. Strength of yarn is also required.
Generally, the sea component polymer used for the sea-island type conjugate multifilament usually includes easy soluble copolymerized polyester. Because it is possible to dissolve the sea component using an alkali aqueous solution and weight reduction facility, which are widely used in weight reduction process of a general polyester fabric, without using an organic solvent, which needs a special apparatus and a lot of recovery cost.
In case that the island component polymer is nylon, upon dissolving of the sea component, the nylon is not degraded by the alkali aqueous solution very well, so the dissolution speed of the sea component is not very important. In case that the island component is polyester, because the polyester is weak to alkali, if the dissolution rate of the sea component is low, the island component is degraded before the sea component is completely dissolved, thus sharply reducing the yarn strength. Due to this, the raising property becomes poor and it is difficult to achieve a desired appearance and touch of a final product.
On the contrary, if the dissolution rate of the sea component is high, the above problems can be prevented and also alkali concentration and dissolution temperature and time can be reduced, thereby reducing the cost for dissolution and increasing productability.